1. Technical Field of the Invention
The present invention relates in general to routing of data in mobile telecommunications systems, and in particular to bearer selection in cellular systems.
2. Description of Related Art
Many cellular telephone networks support the transmission of short message service (SMS) messages between short message entities, such as mobile stations and short message terminals. The purpose of a short message service is to provide a means for transferring textual messages or other types of data messages between the short message entities using the communications environment provided by a cellular telephone network.
Generally, such short message service messages originate or terminate at a subscriber mobile station. In particular, an SMS message is delivered from an originating short message entity to an SMS message center via a fixed telephone network and/or a cellular telephone network. The message center serves as a store and forward center for receiving and delivering SMS messages to a destination short message entity. Upon receiving an SMS message intended for the destination short message entity, the SMS message center forwards the message to that entity.
Because of higher than anticipated demand, SMS traffic has grown at a rapid rate. In existing mobile systems, the only way to cope with increases in SMS traffic is to install additional base station and switching equipment. Unfortunately, it is nearly impossible to expand the system fast enough to keep up with the growing demand. As a result, the SMS traffic can cause severe congestion in the mobile system. This problem is exacerbated by the fact that the use of SMS as a bearer for data transmissions competes with usage of the same channel for voice communications. Thus, SMS congestion can displace voice traffic, thereby reducing the capacity for voice calls below an acceptable service level. Similarly, it is anticipated that new data communication capabilities will also place strains on the available packet data resources. In some cases, packet data networks might become so congested that the capacity for data traffic is reduced below an acceptable level.
There is a need, therefore, for a method and system for reducing congestion in a mobile telecommunications network. Preferably, such a method and system would result in an efficient allocation of bearer resources and would reduce the likelihood that voice calls or data connections are displaced by SMS or other data traffic.
The present invention comprises a method and system for selecting between a circuit-switched network and a packet-switched network for a transmission of data. In accordance with one embodiment of the method, when a request to deliver data to a mobile station is received in a node of the circuit-switched network, the node identifies whether the mobile station has the capability to receive data via one or more packet data bearers. If the mobile station does have such a capability, the node further determines whether the data should be delivered using one of the packet data bearers in the packet-switched network instead of using a circuit-switched bearer. This determination can be made based simply on whether packet data bearers are available or based on an analysis of the current resource and load situation in the bearer sub-systems. Assuming that the node determines that the data should be delivered using a packet data bearer, the data is rerouted to the packet-switched network for delivery to the mobile station.
In accordance with an alternative embodiment of the method, when a request to deliver data to a mobile station is received at a node in the packet-switched network, the packet-switched node determines whether the data should be transmitted via a circuit-switched bearer instead of using a packet data bearer. The determination can be made based on the resource and load situation in the bearer sub-systems. If a circuit-switched bearer is to be used, the packet-switched node reroutes the data to the circuit-switched network for delivery to the mobile station.
The system of the invention includes a circuit-switched network that supports transmission of data via circuit-switched bearers and a packet-switched network that supports transmission of data via packet data bearers. A first switching node is located in one of the networks and a second switching node is located in the other of the networks. The first switching node selects between the networks for delivery of particular data to a mobile station. If the first switching node selects delivery using the other network, the data is rerouted to the second switching node via an interconnection between the circuit-switched and packet-switched networks. The second switching node then selects a particular bearer for transmitting the data and sends the data to the mobile station using the selected bearer. The delivery selection is based on the resource and load situation in the networks.